Now it's snapped up a secret weapon in the social media battle to host photos: Nik Software, a Germany and San Diego-based software company that specializes in photo editing and is the parent of popular iOS photo editing app Snapseed.

Snapseed is a handy photo editor which offers similar filters to Instagram, and a lot more, including the ability to crop, sharpen, blur and play around with the specifics of lighting in a photo. The acquisition suggests that Google+ might be pitching itself as a home for more serious photo enthusiasts. While Facebook and Instagram typically compress photo sizes to save on server space, Google+ already offers high-resolution image uploads as well as photo editing features (such as sharpening or adding text) from within the social network.

News of the acquisition was first reported by The Verge, which points out that while Nik has created quite a few apps for photographers, it struck gold with Snapseed. The $4.99 app gained more than 9 million users during its first year on sale, and was named Apple's iPad App of the Year in 2011.

One reason we can presume Google wants to integrate Nik's technology into its social network: the acquisition was announced by the man behind Google+ himself, Vic Gundotra, on a Google+ post. "We want to help our users create photos they absolutely love, and in our experience Nik does this better than anyone," he wrote.

The same post also talked about the growth of Google+ users, saying the network now had more than 400 million signups, with 100 million of them "monthly active users."

Financial terms of the deal are undisclosed, though it's unlikely to be anywhere near the $1 billion Facebook paid for Instagram, which according to Mark Zuckerberg now has upwards of 100 million users. Nik released a short statement on its site, though, saying, "We’ve always aspired to share our passion for photography with everyone, and with Google’s support we hope to be able to help many millions more people create awesome pictures."

It's unclear if Snapseed will retain its name as a standalone application, or if its editing technology will be folded into that other famous photo editor: Google's Picasa.